Reductive pyrolysis study of sulfur compounds in different Tabas coal samples (Iran)

A comparative study of the effects of mineral and pyrite removal on the determination of organic sulfur functionalities in representative, as well as its low and high sulfur analogue samples of Tabas coal (C1 seam) were studied by atmospheric pressure–temperature-programmed reduction (AP-TPR) method. The AP-TPR investigation showed the presence of di-aryl sulfides, aryl–alkyl sulfides, simple and complex thiophenic structure in all representative, low and high sulfur samples. There is no indication of the presence of pure di-alkyl sulfides, disulfides or thiols, nor oxidised sulfur forms in the samples. Only minor differences in sulfur functionalities were detected qualitatively between the three analogue samples. Quantitatively differences in sulfur forms were found to be more pronounced. The presence of CH fragments on gases emitted during AP-TPR investigation of demineralised and demineralised pyrite-free samples, shows evidence for the formation of shorter CH chains and of polyaromatic compounds, and lower molecular weight material in the demineralization and pyritic sulfur removal stages.